Semiconductor image sensors are used to sense radiation such as light. Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) and charge-coupled device (CCD) sensors are widely used in various applications such as digital still camera or mobile phone camera applications. These devices utilize an array of pixels in a substrate, including photodiodes and transistors, that can absorb radiation projected toward the substrate and convert the sensed radiation into electrical signals.
A back side illuminated (BSI) image sensor device is one type of image sensor device. These BSI image sensor devices are operable to detect light from its back side. A BSI image sensor device has a relatively large step-height between a device region of a wafer and a bond pad region. This step height may lead to etching difficulties when bond pads are formed, which may induce leakage between adjacent bond pads through a sidewall of the wafer. Such leakage degrades BSI image sensor device performance and is therefore undesirable.
Hence, while existing methods of fabricating BSI image sensor devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.